有3个实体:1)Question，2)Tag和它们之间的连接表-Question_Has_Tag
除联接表外，Java中的对象相同。 取而代之的是:
public class Question {
//
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "question_has_tag",
joinColumns = @JoinColumn(name = "question_id"),
inverseJoinColumns = @JoinColumn(name = "tag_id"))
private List<Tag> tags;
public class Tag {
//
@ManyToMany(mappedBy = "tags", fetch = FetchType.LAZY)
@ContainedIn
private List<Question> questions;
要转换的查询是:
select * from question as q
join question_has_tag as qht on q.id = qht.question_id
where qht.question_id in (select question_id from question_has_tag where tag_id = 1);
我混淆了联接表和集合。 把一个转化成另一个
如果你需要更多的代码或信息，请让我知道
试试这个:
@Entity
public class Question {
@ManyToMany(mappedBy = "question_has_tag", fetch = FetchType.LAZY)
private List<Tag> tags;
}
@Entity
public class Tag {
@ManyToMany(targetEntity = Question.class, fetch = FetchType.LAZY)
private List<Question> questions;
}
和存储库:
@Repository
public interface QuestionRepository extends JpaRepository<Question, Integer> {
@Query("select q from Question q join Tag t where q.id in (:ids)")
public List<Question> getQuestionsById(@Param("ids") List<Integer> ids);
}
